Patent Application
20060037756
The present invention relates generally to a method and apparatus for installing insulation on subsea oil and gas flowlines, connectors and other equipment.
Subsea oil and gas wells are constantly exposed to cold seawater that can often times be just a few degrees above freezing. Subsea oil production often leaves the well at much higher temperatures, sometimes exceeding 300 degrees Fahrenheit. When the flow of oil is interrupted for any reason, the production fluid in the flowline begins to cool. If the production fluid was allowed to sufficiently cool, oil production could be completely stopped due to the formation of hydrates or paraffin blocks that can form in the flowline and connectors, inhibiting resumption of the flow of the fluid.
It is therefore desirable to insulate the subsea production flowline connectors to maintain the much hotter temperature of the oil and gas production. This is commonly done with rigid covers, commonly referred to as “dog houses” in the industry. These dog houses are placed around the flowline connectors or other equipment to be insulated, and have proven to do a less than adequate job of insulation. However, one key disadvantage of using dog houses is that because they are rigid covers, seawater is able to flow through gaps between the cover and the insulated flowline or equipment. This water flow allows heat to escape, thereby reducing the effectiveness of the insulation.
It would therefore be desirable to develop a system that can install insulation on subsea flowline, connectors or equipment without reducing the effectiveness of the insulation.
Provided herein is a system and apparatus for installing subsea insulation on subsea flowlines, connectors and equipment. This system provides a lightweight, thin mold designed and built to suit the parameters of the subsea item to be insulated. The mold fits and seals around the area to be insulated, and is then injected with an insulation material by a remotely operated vehicle (ROV). The insulation material is injected as a liquid solution, thereby avoiding the presence of gaps in the insulation. This liquid solution is a combination of an insulation solution and a catalyst mixed together during the injection process. The mixture is then allowed to solidify, forming the molded insulation.
One embodiment of the present invention first uses a subsea gel insulation mold. This mold is a pre-engineered fiberglass, plastic or metal enclosure, the purpose of which is to fit around the subsea flowline, connector or other equipment to be insulated. Generally, the mold will comprise a hinged enclosure that is closed and secured around the item to be insulated. In one embodiment, the mold comprises gaskets to provide a tight seal between the mold and the item to be insulated. The mold can either be preinstalled on the flowline, connector or other equipment to be insulated, or it can be installed by a remotely operated vehicle (ROV). The process of installing the subsea gel insulation mold with an ROV involves deploying the ROV to the site of the item to be insulated, and using the ROV to install the mold. In one embodiment, the mold is attached to the ROV itself, however if multiple molds are needed, a separate mold deployment skid can be provided to supply the multiple molds.
Also provided is a subsea insulation solution reservoir skid, which is deployed separately from the ROV in the vicinity of the subsea insulation installation site. The subsea insulation solution reservoir skid comprises a flexible insulation solution reservoir and a hose for delivering the insulation solution.
One embodiment of the present invention involves the use of a subsea gel injection system. This system is a remotely operated package integrated within the frame of the ROV, or provided as a separate skid mounted under the ROV, depending upon the number of injection molds to be filled and the insulation solution/catalyst ratio provided. The subsea gel injection system comprises a pump module, which itself comprises separate pumps for the insulation solution and the catalyst. The system also uses a mixing nozzle with an injection hose fitted with a single port hot stab for mixing the insulation solution and catalyst upon injection of the mixture into the mold installed around the subsea flowline, connector or equipment to be insulated. Finally, the system comprises a catalyst reservoir for containing the catalyst prior to its injection into the mold.
In one method of the present invention, the insulation solution is pumped into the flexible bladder on the subsea insulation solution reservoir skid, and the catalyst is pumped into the catalyst reservoir on the subsea gel injection system skid. The pump module of the subsea gel injection skid is connected to the ROV system so as to draw power from the ROV system. For instance, if the pumps are hydraulic pumps, then they are connected to the ROV hydraulic system, however if the pumps are electric, then they would be connected to the ROV electrical system. The mixing nozzle is then connected to the pump module, and the injection hose and hot stab are installed near the ROV manipulator. The molds are either installed on the ROV skid or on the separate mold deployment skid, along with the mold installation tool.
The insulation solution reservoir and mold deployment skids are lowered from the water surface to the sea floor on separate surface deployed lift lines and placed near the work site. The ROV, such as, for example, the INNOVATOR® manufactured by Sonsub Inc. of Houston, Tex., is then launched and lowered to the work site. The process of installing the insulation can then begin.
First, the ROV flies to the mold deployment skid and uses its manipulator to connect a hydraulic hot stab to the mold installation tool. The ROV grab arm then picks up the mold installation tool and maneuvers the installation tool over a mold on the mold deployment skid. The hydraulic hot stab powers the installation tool to grab the mold and disconnect the mold from the skid. The ROV then flies the mold over to the flowline, connector or other equipment to be insulated, where the installation tool locks the mold around the flowline, connector or other equipment to be insulated.
The ROV then returns the installation tool to the mold deployment skid, after which the ROV flies to the insulation solution reservoir skid. The ROV pulls the hose on the insulation solution reservoir skid over to the area of the mold, and then uses its manipulator to connect the insulation solution reservoir hose hot stab to the gel pump. The ROV manipulator then connects the mixing nozzle hose to the mold receptacle, and starts up the catalyst and insulation solution pumps to pump the catalyst and insulation solution through the mixing nozzle and into the mold. After the mold is filled with the insulation solution/catalyst mixture, the catalyst pump is disengaged, and a small quantity of insulation solution is pumped through the mixing nozzle to clean out the mixed solution, preventing insulation gel from curing and hardening within the mixing nozzle. The ROV manipulator then disconnects the injection hose, and is now ready to install the next mold. Once all the molds are installed, the ROV, mold skid, and insulation solution reservoir skid are recovered to the surface.
Insulation gel for use in the present invention is known in the art. One type of the insulation gel described above, in which an insulation solution is mixed with a catalyst upon injection into the mold, is DEEPGEL(TM) offered by Ythan Environmental Services Ltd. However, any type of insulation that is injectable into a mold and allowed to cure or harden can be used in the present invention. Some such insulations may not require the use of a catalyst for hardening the insulation, in which case there would be no need for a catalyst container or catalyst pump, thereby reducing the amount of equipment to perform the method and build the apparatus of the present invention.
While the apparatuses and methods of the present invention have been described in terms of preferred embodiments, it will be apparent to those of skill in the art that variations may be applied to what has been described herein without departing from the concept and scope of the invention. All such similar substitutes and modifications apparent to those skilled in the art are deemed to be within the scope and concept of the invention as it is set out in the following claims.
